re PR middle-end/77594 (double computation for __builtin_sub_overflow (0, ...))

	PR middle-end/77594
	* internal-fn.c (expand_arith_overflow) <case MINUS_EXPR>: Don't fall
	through into expand_addsub_overflow after expand_neg_overflow.

	* gcc.target/i386/pr77594.c: New test.

Co-Authored-By: Eric Botcazou <ebotcazou@adacore.com>

From-SVN: r240173

gcc/ChangeLog

+2016-09-16  Jakub Jelinek  <jakub@redhat.com>
+	    Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR middle-end/77594
+	* internal-fn.c (expand_arith_overflow) <case MINUS_EXPR>: Don't fall
+	through into expand_addsub_overflow after expand_neg_overflow.
+
 2016-09-15  David Malcolm  <dmalcolm@redhat.com>
 
 	* diagnostic-show-locus.c

gcc/internal-fn.c

@@ -1833,7 +1833,10 @@ expand_arith_overflow (enum tree_code code, gimple *stmt)
 	    {
 	    case MINUS_EXPR:
 	      if (integer_zerop (arg0) && !unsr_p)
+		{
 		  expand_neg_overflow (loc, lhs, arg1, false);
+		  return;
+		}
 	      /* FALLTHRU */
 	    case PLUS_EXPR:
 	      expand_addsub_overflow (loc, code, lhs, arg0, arg1,

gcc/testsuite/ChangeLog

+2016-09-16  Jakub Jelinek  <jakub@redhat.com>
+	    Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR middle-end/77594
+	* gcc.target/i386/pr77594.c: New test.
+
 2016-09-15  Louis Krupp  <louis.krupp@zoho.com>
 
 	PR fortran/69963

gcc/testsuite/gcc.target/i386/pr77594.c

+/* PR middle-end/77594 */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+int
+foo (int a, int *b)
+{
+  return __builtin_sub_overflow (0, a, b);
+}
+
+/* { dg-final { scan-assembler-times "\tjn?o\t" 1 } } */